Recently there has been wide use of gas-permeable molded refractory bodies, generally termed as gas scavengers, for injecting various gases through the refractory lining into metallurgical furnaces and containers in connection with processing of molten metals. These gas scavengers are normally located in the base, especially in converters for refining of crude [pig] iron; in pig-iron ladles; casting ladles, and tundishes used in continuous casting of steel. They may also be built into all these units and also into the lining of the lateral walls of other metallurgical furnaces and containers, for instance into electric arc furnaces. In all these cases the gas scavengers should meet the requirement that their durability be not less than that of the adjacent refractory lining in the furnace or container, so that downtime caused by a premature wear of such gas scavengers can be avoided or at least minimized. To meet this requirement, two principal alternatives are available. One is the improvement of the characteristics of the refractory material used in the construction of the gas scavengers; the other is the improvement in the construction of the scavengers. The present invention is directed to the second alternative.
Various attempts have already been made to improve the durability of the gas scavengers, which are generally disposed in a ventilated brick. For instance, a gas scavenger is known which is lined on its lateral walls and on its base with sheet metal. Metal plates extend through its interior. The end opposite from the interior of the furnace or container (the cold end) constitutes the base of the scavenger, and includes a gas injection pipe for conducting gas through the scavenger into the melt to be treated. On this gas conduit pipe there is attached a spiral-shaped pipe for conducting the scavenging gas. The gas conduit pipe and the spiral-shaped pipe are embedded in a sintered refractory material (FR-OS No. 24 51 945). The spiral-shaped pipe in this construction is supposed to solidify the melt on the pipe. This reduces wear of the gas scavenger and damage to the sheet metal at the hot end of the gas scavenger. This also prevents flow of molten material into the ventilated brick, and by the solidification of a portion of the melt prevents any further flow from the metallurgical furnace or container. This type of known gas scavenger, however, has the disadvantage, that it is not readily replaceable. This results in interruption of the production of the furnace or container, because, in spite of precautions taken, such scavengers are subject to faster wear than the adjacent refractory lining.
One object of invention is to provide a safety system for metallurgical furnaces and containers, which precludes the possibility of a break-through of the melt through a gas scavenger. A further object of the invention is to facilitate the simple replacement of such a gas scavenger. This was found to be possible when the gas scavenger is constructed in a special manner together with a block of refeactory material in a refractory lining, and further, when the conduit pipe for feeding the processing gases for the melt to the gas scavenger is constructed in a special manner. Accordingly, the invention is directed to a metallurgical furnace or a metallurgical container for handling of molten metal, having at least one gas scavenger disposed in its refractory lining, preferably at the base. The end of the gas scavenger distant from the interior of the furnace or container (the gas scavenger base) has a gas conduit pipe therein and a spiral-shaped pipe for conducting the scavenging gas is connected to it. The base of the gas scavenger is set into a recess of a base block of refractory material. Preferably, the pipe system in the base block is spirally-shaped and is constructed from a double, partially vertical convoluted pipe embedded in the block-like base.
A preferred embodiment of the invention has the gas scavenger, with its base in a recess in a base block, it being secured with a refractory mortar or cement constructing a labyrinth-type seal. Thus, any further breakthrough of molten metal, which may have penetrated between the gas scavenger and the immediate surrounding refractory lining or between the gas scavenger and the sheet metal mantle encasing it, can be prevented. Generally, it is practical to dispose the gas scavenger in a ventilated brick. In case the melt reaches the gas conduit pipe, it must then rise upwards in the double, partially vertical convoluted portions of the pipe. The melt will not rise into the vertical portions of the pipe, but rather will solidify therein. This solidification is promoted by the configuration of the double spiral pipe system. The flow of the melt into each portion of the double spiral is divided, and this divides the heat of the melt and increases its surface area so that the metal solidifies at a faster rate than molten metal passing through a single conduit. The increased solidification rate and the resistance to flow provided by the vertical portion of the double spiral combines to effectively inhibit the flow of the melt as it rises in the vertical portions of the double spiral conduit. The solidification of the metal in the pipe can also be promoted by constructing the pipe system of a highly heat conductive material. It is also preferred that the material of the pipe system have a lower melting point than that of the metal being processed in the furnace or container. Furthermore, it is also possible to decrease the pipe diameter of the convoluted pipe without fear of reducing the gas flow through the gas scavenger into the melt, as it would be the case in a gas conduit consisting of an ordinary pipe.
The connection between the gas conduit pipe of the gas scavenger and the pipe system can be carried out in an unusual manner suitable for such purposes, for instance by means of a screw or plug coupling.
As refractory materials for the construction of the fused base block, materials having high aluminum oxide contents are preferred, however, materials such as magnesium oxide, magnesium oxide-chromium ore, olivine [chrysolite], zirconium silicate, and others, may also be considered suitable.
It should be noted that as gas scavengers either bricks having a normally increased porosity, or bricks having a so-called directional porosity, that is, bricks in which a number of pores are aligned in a desired direction throughout the whole brick, may be used. To obtain a high durability, the bricks with a directional porosity have proven to be specially beneficial.